Is it normal to be bitter about this?

I get so bitter about all my friends having babies, and cant help but think "why do they get to? They arent married, they werent planning it, it was just a suprise! So when they find out that they are pregnant its all they talk about and suddenly have symptoms that werent there before, and when the baby is born its non stop blabbing about their baby and constant pics and updates about spit up and poop! Part of me is annoyed at how they wont shut the heck up, part of me is angry and bitter because of my struggle with getting pregnant, and then part of me wants to scream because oh how they think they just know everything about children now and I have no right to say anything about the subject because what would their childless friend know?! I wanna be happy for them, but I feel so alienated and frustrated with their sudden and unexpected especially since not one of them is married and trying to concieve pregnancies, and how they make me feel about it. Its so hard to stay friends even with ur best friend once they have a baby becuase most of them change and not in a good way. Is it normal to be so bitter about all this, or am I just terrible to feel this way? I just hope once I finally have a baby that I dont lose myself, because its so important to me to not act like that kind of person and become a hypocrite.